Recently, due to limitation of land transportation caused by the rapid increase of automobiles and severe congestion of road transportation, demands for electric railways are increasing day by day.
Meanwhile, according to the supply expansion to meet the increasing demand for electric railways, there is a pressing need for securing the safety and reliability of the electric railway as massive public transportation means.
The vehicle of the electric railway receives electric energy of AC 25,000V or DC 1,500V required as the operating power from a contact wire (also called as a ‘trolley wire’) installed along the track of the railway and this electric energy is utilized to operate and control the vehicle. To this end, a pantograph for collecting the power is installed on the vehicle.
As shown in FIG. 1, the conventional electric railroad vehicle 1 or trolleybus is configured such that a pantograph 20 is in direct contact with a contact wire to feed with the power required for the vehicle into the vehicle.
However, since the contact wire 10 and the pantograph 20 are in contact with each other, a power collecting plate (contact strip) of the pantograph 20 and the contact wire 10 may be worn out. Therefore, it is necessary to periodically maintain and repair the power collecting plate of the pantograph 20 and the contact wire 10.
In addition, in order to prevent a contact wire from being separated from the pantograph, it is necessary to accurately control the pantograph 20 to maintain a constant uplift force. In particular, at a high-speed driving time, it is quite difficult to attain a uniform uplift force, which may hinder speed improvement of a high speed train and may lead to an environmental problem, such as an aerodynamic noise.